Question about B&K AVR-202

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Well where do I begin. First, the polarity switch on the back might eliminate or reduce the hum, but by todays standards the way it functions is a deadly safety hazard (remember all the musicians that got fried in the '60's and early '70's?). That circuitry should be disabled and the unit retrofitted with a 3 prong power cord.

Next, the tube filiments are powered by AC voltage, and there is a control on the chassis for balancing it in order to reduce the hum. It could be toast or mis-adjusted. There could be a tube or other component problem causing your hum. The DC power supply could have faulty filter capacitors.

Another source of problems in these amps are the carbon resistors that introduce static noise in the audio. These should be changed to much better carbon film resistors.

If you are not comfortable working on electronic equipment with voltages in excess of 300VDC you should bring it to a pro audio repair shop.

Posted on Apr 28, 2009

  • rjivaro Apr 28, 2009

    But wait. There's more.
    First, I hope I didn't scare you. The fix for the safety issue is an easy one, but is important. The bassman amp series are wonderful classic amps and well worth the few repairs and upgrades that will make them a peak performer.

    Another issue is the sovtek tubes. The softer vacuum of soviet tubes sound great in preamps and guitar amps, but personally I have always liked the sound of the harder vacuum that american made tubes had (no longer in production). Try Groove Tubes if you want a tighter and punchier sound from the amp.
    Or maybe you will get lucky and find some old (slightly used or unused) Sylvania's.



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